This application claims the priority of Swiss application 964/99, filed in Switzerland on May 25, 1999, the disclosure of which is expressly incorporated by reference herein.
In such control systems, the control quantity (ACTUAL value measurement) is detected by measuring the plasma light emission, for example, in the case of a specific spectral line, by measuring the target voltage. A DESIRED value is defined for the measured control quantity and, corresponding to the control deviations, for example, the flow of reactive gas, in the above-indicated example, the oxygen flow (or, if it is not detected as a control quantity, the target voltage) is set as a regulating quantity in the control circuit. As a result, the operation, particularly a stabilization of the process in the desired working point, for example, in the above-mentioned transition mode, is achieved.
FIGS. 1 to 4 are schematic views of typical vacuum treatment systems of the latter type. They are systems of this type and workpiece manufacturing processes which can be implemented by vacuum treatment systems of this type and at which the problems to be described were recognized and solved according to the invention. The solutions according to the invention can, however, basically be used for systems and processes of the initially mentioned type in which the treatment process or the treatment atmosphere is controlled.
As illustrated by the arrow 4, substrates 1 are moved in a workpiece carrier drum 3 rotating in a treatment chamber past at least one sputtering source 5. The sputtering source 5 with the metallic, thus electrically highly conductive target is, normally constructed as a magnetron source, DC-operated; often additionally with a chopper unit connected between a DC feeder generator and the sputtering source 5, as described in detail in EP-A-0 564 789, also incorporated by reference herein. A chopper unit intermittently switches a current path situated above the sputtering source connections to be of high resistance and low resistance.
In FIGS. 1 to 4, the DC generator and the optionally provided chopper unit are each illustrated in the blocks 7 of the sputtering source feed. In addition to a working gas GA, such as argon, a reactive gas GR, such as oxygen O2, is admitted to the treatment atmosphere U of the vacuum chamber, the reactive gas GR particularly by way of gas flow regulating valves 10.
Above the sputtering sources 5, a reactive plasma 9 is formed in which the substrates and workpieces 1 moved through by the drum 3 above the sputtering surfaces are sputter-coated. Because not only the substrates 1 are coated with the electrically poorly conductive reaction products formed in the reactive plasma 9 but also the metallic sputtering surfaces of the sputtering sources 5, the coating process described so far, particularly for achieving coating rates which are as high as possible, is unstable. For this reason, particularly in the case of these treatment processes and systems, the treatment process and, in this case, actually the treatment atmosphere acting upon the workpieces 1, is stabilized in the treatment area BB with a control.
As a possible implementation embodiment of such a control circuit according to FIG. 1, a plasma emissions monitor 12 measures the intensities of at least one of the spectral line or lines characteristics of the light emission from the reactive plasma 9. These intensities are fed as a measured control quantity Xa to a controller 14a.
In FIG. 2, the target voltage on the sputtering source 5 is measured as the measured ACTUAL quantity Xb of the control circuit by a voltage measuring device 16 and is fed to a controller 14b. With respect to the detection of the measured control quantity X, FIGS. 1, 3 and 2, 4 correspond to one another. At the controllers 14a and 14b, for forming control differences, the respective measured control quantities Xa and Xb are compared with the preferably adjustable guide values Wa and Wb, which correspond to the measured control quantities.
In accordance with the formed control differences at the controllers 14a and 14b and their amplification on transmission paths (not illustrated separately) dimensioned with respect to the frequency response according to the rules of control engineering, regulating signals S are generated at the output side of the controllers 14. As seen in FIGS. 1 and 2, the regulating signals, correspondingly marked Saa and Sba, are guided to the flow control valves 10 for the reactive gas as regulating elements which are set such that the respectively measured control quantities Xa and Xb are led to the values defined by the guide quantities Wa and Wb and are held there.
As seen in FIGS. 3 and 4, the regulating signal generated on the output side of the controllers 14a and 14b, which is correspondingly marked Sab and Sbb, is fed to the sputtering source feeds 7 which now themselves act as control regulating elements. This takes place either at their DC generators and/or at their optionally provided chopper units, where the chopper duty cycle is set.
The systems illustrated, for example, by FIGS. 1 to 4 are therefore vacuum treatment systems with a vacuum chamber, having elements for establishing a treatment atmosphere (specifically particularly a sputtering source and reactive gas feeds), and a sensor arrangement for detecting the treatment atmosphere momentarily existing in the chamber, the plasma emissions monitors and voltage measuring devices described as examples. The sensor arrangements ACTUAL-value sensors of at least one of the mentioned elements form a regulating element of one control circuit respectively for the treatment atmosphere.
For depositing electrically poorly conducting or non-conductive layers by way of the release of one layer material component of electrically conductive targets, an approach described in U.S. Pat. No. 5,225,057 involves first carrying out the metallic coating in spatially separated treatment stages and then oxidizing it in a reactive gas stage (an oxidation stage). In this known approach, there is no stability problem with respect to the coating process, but the system configuration consisting of several stages used for this purpose is relatively complicated.
As mentioned above, the present invention is based on treatment systems and manufacturing processes of the type explained by reference to FIGS. 1 to 4. It was demonstrated there that, particularly in the case of wide substrates of a width B larger than the dimension A in the same direction, preferably five times larger, and/or in the case of a small diameter of the substrate drum 3, along the substrate width B, because of the non-linear movement of the substrates in the area BB and relative to the sputtering source 5, a pronounced, approximately parabolic layer thickness distribution is obtained, as illustrated in FIG. 11a. This layer thickness distribution is known as a so-called “chord effect”.
The effective width of a substrate is its linearly measured dimension in the direction of its relative movement to the sputtering source 5. The corresponding effective sputtering source dimension A is its linearly measured dimension in the same direction. Furthermore, the above-mentioned substrate width B can definitely be taken up by several side-by-side smaller substrates. The addressed substrate 21 will then actually be a batch substrate.
In addition, it is stressed at this point that, for example, with a view to FIG. 1, the substrates may definitely be arranged on the interior side of a revolving carousel, which revolves around a sputtering source arrangement on a path which will then be concave with respect to the sputtering source arrangement. All foregoing statements and all following statements which are based on the drum arrangements according to FIGS. 1 to 4 analogously apply to the full extent to concave workpiece movements with respect to the sputtering source.